1. Field of the Invention
The present invention relates to a middle ear hearing aid transducer which can be easily introduced into the middle ear, and whose sensitivity can be maintained after extensive use without contamination by foreign substances.
2. Description of the Related Art
Many types of hearing aids are available including an external type which is disposed in the external auditory canal or behind an auricle, and an inner and middle ear implant types which are accompanied with surgery. In addition, there are temporal bone conduction hearing aids which produce mechanical vibrations from sound waves and transmit the mechanical vibrations to the inner ear via a temporal bone. In particular, middle ear implant hearing aids are extensively used to remedy moderate or extreme hearing loss or sensorineural hearing loss.
FIG. 1 shows a conventional middle ear hearing aid whose transducer is implanted into a patient""s staples, and FIG. 2 is a perspective view of the transducer of FIG. 1. As shown in FIG. 1, the conventional middle ear hearing aid includes an external unit 10, which is worn behind the patient""s auricle, and an internal unit 20, which is implanted in the outer ear and middle ear. In particular, the external unit 10 includes a microphone 11, amplification circuitry 12, a battery 13, and an external coupling coil 14. The internal unit 20 includes internal circuitry (not shown) adjacent to the external coupling coil 14, an internal coupling coil 24, and a transducer 25, which is implanted into a stapes 8 or malleus 9 of the ossicular chain in the middle ear.
Referring to FIG. 2, the transducer 25 includes a coil portion 26 fixed to a bone of the middle ear and a permanent magnet 27 implanted into the stapes 8 or malleus 9. The coil member 26 includes a support 26a fixed to a bone of the middle ear and a coil 26b supported by the support 26a and facing the permanent magnet 27. As sound waves are converted into electrical signals by the internal coupling coil 24 and transmitted to the coil 26b, the coil 26b generates a magnetic flux to vibrate the permanent magnet 27 implanted into the stapes 8.
In the hearing aid having the configuration described above, the microphone 11 and the amplification circuitry 12 of the external unit 10 receives and amplifies external sound waves. The amplified sound waves are transformed into electrical signals and transmitted to the external coil coupling coil 14. The external coupling coil 14 generates electromagnetic waves corresponding to the electrical signals and transmits the electromagnetic waves to the internal coupling coil 24. The internal circuitry converts the transmitted electromagnetic waves into electrical signals and transmits the electrical signals to the coil portion 26. The coil portion 26 generates a magnetic flux corresponding to the electrical signals to vibrate the permanent magnet 27 and the stapes 8 or malleus to which the permanent magnet 27 is fixed. Through these processes, a patient having a hearing disorder can perceive sound transmitted from the outside.
In the transducer 26 having the configuration described previously, the coil 26b, which generates the magnetic flux, is an air-core coil supported by the support 26a. The magnetic flux generated by the coil 26b is not capable of causing large vibrations in the permanent magnet 27. Thus, the transducer 26 with the air-core coil is not suitable for a patient with a serious hearing disorder.
To increase the magnetic flux, an iron core can be inserted into the coil 26b. In this case, even when no signal is input to the coil 26b, a stress is exerted upon the ossicular chain due to continuous attraction between the iron core and the permanent magnet 27 fixed to the ossicles. The ossicular chain, which is a highly sensitive organ of the body, is susceptible to damage caused by the attractive force between the permanent magnet 27 and the iron core. If the damage is serious, the sound wave transmission path may deform close to the entrance of the inner ear.
The coil 26b and the permanent magnet 27 are spaced a predetermined distance a part. The gap between the coil 26b and the permanent magnet 27 should be kept constant to allow the permanent magnet 27 to vibrate. If a fluid or foreign substance sticks to the coil 26b or the permanent magnet 27, the gap becomes narrower, interrupting vibrations of the permanent magnet 27. As a result, a patient who has a hearing disorder will not be able to perceive sound. Thus, there is a need for the gap between the coil 26b and the permanent magnet 27 to be kept constant even after extensive use.
In addition, in the conventional hearing aid having the configuration described above, the support 26a for the coil 26b and the permanent magnet 27 are implanted into bones in the middle ear by surgery, increasing concern about deformation of the middle ear. Thus, there is a need for a hearing aid which can be easily mounted into the middle ear without causing deformation of the middle ear.
To address the above limitations, it is an object of the present invention to provide a middle ear hearing aid transducer which can be kept sensitive to a small sound wave without contamination by fluid or foreign substance.
It is another object of the present invention to provide a middle ear hearing aid transducer which can be easily introduced into the middle ear without causing deformation of the sound wave transmission path.
The objects of the present invention are achieved by a middle ear hearing aid transducer comprising first and second permanent magnets arranged such that the same poles face each other; a coil separated a predetermined distance from the outer surfaces of the first and second permanent magnets, and surrounding the first and second permanent magnets; a case for accommodating the first and second permanent magnets and the coil; and a vibration member for supporting the first and second permanent magnets to keep a predetermined distance between the coil and the outer surfaces of the first and second permanent magnets, and for transmitting vibrations of the first and second permanent magnets to the case.
It is preferable that the vibration member comprises: a circular plate interposed between the first and second permanent magnets in the case; and supports disposed on the circular plate for supporting one end of the first and second permanent magnets, and the vibration member is an elastic member for suspending the first and second permanent magnets separated from the coil in the case. It is preferable that the circular plate and the supports are formed as a single unit.
Alternatively, the vibration member may comprise first and second vibration members interposed between the ends of the case and one end of the first and second permanent magnets, respectively, and the vibration member may be an elastic member for suspending the first and second permanent magnets separated from the coil in the case.
Alternatively, the vibration member may comprise first and second vibration members having a plurality of holes and interposed between the ends of the case and one end of the respective first and second permanent magnets, respectively, and the vibration member may be an elastic member for suspending the first and second permanent magnets separated from the coil in the case.